1. Field of the Invention
The present invention relates to the field of photography and, more particularly, to self-developing cameras including a mounting apparatus for a spreader system which operates to distribute a fluid processing composition within an exposed film unit of the self-developing type.
2. Description of the Prior Art
An important step in the processing of a self-developing type film unit having a photosensitive element is the distributing of a fluid processing composition between a predetermined pair of layers of the film unit, subsequent to exposure, to initiate a development and diffusion transfer process. In order to optimize the process, the processing composition must be uniformly distributed over an entire exposed area of the photosensitive element.
In a typical "peel apart" arrangement, a sheet of photosensitive material is first exposed to image-carrying light rays entering through a lens system of a camera to form a latent image therein. This sheet is subsequently progressively pressed against an image-receiving sheet with a predetermined quantity of a viscous processing fluid being disposed therebetween. The fluid may initially be releasably stored in a rupturable pod attached to one of the sheets. As the film unit comprising such sheets and pod is advanced between a pair of juxtaposed pressure-applying members, a compressive force is exerted upon the film unit which first ruptures the pod and subsequently spreads the processing fluid in a layer between the superposed sheets. The pressure-applying members may typically comprise either a pair of rollers, one roller and a stationary member, or a pair of rigid stationary members.
The spreading of the fluid processing composition is a critical consideration in producing high quality photographic prints. The quality of the finished print provided by these photographic systems is directly related to the nature of the processing composition coating applied to the photographic sheets. If too heavy a coating is applied, the processing composition may fail to cover the entire image area of the element thereby resulting in an incomplete spread and processing of the photographic print or a "murky" appearing development may occur. If the coating is too thin, the developed photographic print may contain an undesirable reddish hue overall.
Therefore, it is of the utmost importance for a self-developing camera to include a spreading apparatus and a mounting arrangement therefor which facilitates its proper operation and when necessary provides access to the apparatus for a thorough cleaning.
Traditionally, in commercially available systems, the spreading systems are manually operated. A leader attached to a film unit is pulled from the camera to one side of the pressure-applying members for drawing a leading end of the film unit between the pressure-applying members so that the leading end of the film unit may be grasped for withdrawing the film unit from the housing between the pressure-applying members through a film exit slot included in the housing to the exterior of the camera. Spreader systems developed for use with self-developing film of this type are described in detail in U.S. Pat. No. 3,165,039. This spreader system forms a part of a rear body assembly of the camera comprising a door having a frame including a film exit slot fixedly attached by rivets to the door and the spreader system pivotally secured to the frame whereby the spreader system can be pivotally elevated from an operating position to a cleaning position. The pressure-applying members are coupled to the frame such that the pressure-applying members are adjacent to the film exit slot and the point of tangency between the pressure-applying members or bite line between the pressure-applying elements is in alignment with the film exit slot in a natural or normal emerging path of travel of a film unit during its passage therebetween.
The rear body assembly is pivotally attached to the body of the camera and cooperates therewith to complete the forming of a film chamber included within a main body of the camera wherein a film cassette containing a plurality of film units is received. This spreader system is characterized by its conventional construction using a plurality of piece parts that must be sequentially assembled to construct a mounting apparatus which forms a part of the rear body assembly. The rear body assembly includes the spreader system fixedly secured thereto as one component thereof and cooperates with the main camera body to provide the lighttight receiving chamber for the film cassette. The door and the film exit slot are first located relative to the remainder of the film receiving chamber, and then, the pressure-applying members are located in operative relationship to the door, film exit slot, and the film receiving chamber. Therefore, the door operates as a principal member of a combination to which the material to be processed, the exposed film unit, and the processor, the spreader system are keyed due to its participation as a portion of the film receiving chamber and as a mounting apparatus for the spreader system.
U.S. Pat. No. 3,745,904 discloses an improved mounting apparatus for a spreader system which permits the spreader system to be releasably retained upon a rear body member which is pivotally connected to a main camera body. When the rear body member is disposed in an open position with respect to the main camera body access is provided into the interior of the camera for purposes of loading the camera with a film pack containing a sufficient quantity of photographic materials to produce a plurality of photographic prints. The rear body member includes a film exit slot disposed transversely in a forward wall thereof for withdrawing film units therethrough subsequent to their passage between a pair of juxtaposed pressure-applying members.
The spreader system comprises a platform which serves to support and retain the pressure-applying members thereon and further includes a latch which cooperates with a brace included upon an inner surface of the rear body member to releasably retain the pressure-applying members such that a bottom edge of the upper pressure-applying member is adjacent to and aligned with the film exit slot whereby a leading edge of an emerging film unit may continue in a natural or normal emerging path of travel through the film exit slot. The brace is formed in a predetermined location so that the spring latch on the platform bears against an upright surface of the brace and the forward walls of the platform bear against the forward wall of the rear body member thereby preventing longitudinal movement of the spreader assembly upon the rear body member and biasing the pressure-applying members in the direction of the film exit slot. Lateral movement of the spreader system is substantially limited by a snug fit between side members of the platform bearing against pliable side walls of the rear body member.
This mounting apparatus was specifically developed to provide a spreader system which could be quickly inserted into and removed from a location within a camera wherein the pressure-applying members are substantially adjacent to the film exit door and aligned therewith, and further facilitates spreader system cleaning operations. While improving the prior art by its ability to mount the spreader system as an integral assembly and lending itself to high-volume fabrication and assembly techniques, the mounting apparatus was once again a component of the rear body assembly which in turn cooperated with the main camera body to construct the film receiving chamber. As a result, the pressure-applying members are attached upon the door which determines the operative relationship thereof with the film receiving chamber and the film exit slot as evidenced by the fact that upon removal of the rear body assembly from the main body of the camera, in this system and in the previously disclosed system, the receiving chamber and the spreader system for the camera are rendered inoperable.
Representative examples of an integral "non-peel apart" self-developing photosensitive element are disclosed in U.S. Pat Nos. 3,415,644 and 3,594,165. Basically, these integral film units are multilayer structures having a fluid processing composition releasably stored in a rupturable pod or container at a leading end and a trap for collecting excess fluid at a trailing end thereof.
Subsequent to exposure, the film unit is advanced leading end first, between a pair of juxtaposed pressure-applying members for applying a compressive pressure progressively along the length of the photosensitive element thereby spreading the processing composition released from the pod.
The multilayer structure of the film unit includes a pair of outer sheets which are bound together along lateral edges thereof to cooperate with the trap to prevent the fluid processing composition from escaping from between a predetermined pair of layers. Because the lateral edges are bound together, there is more resistance to fluid flow adjacent these edges than in a center portion of the photosensitive element. Consequently, the discharged mass of fluid tends to advance rearwardly along a wavefront with a greater concentration of fluid in the center than out at the lateral edges.
The integral self-developing film unit generally have an inherent stiffness and as the element progressively emerges from between the pressure-applying members in a cantilever fashion, it tends to follow a natural and substantially planar path of travel. It has been discovered that by deflecting the film unit from the natural path of travel, thereby inducing a gentle and large radius bend in the film unit upon emerging from between the pressure-applying members, that the uniformity of distribution of fluid within the film unit is significantly and beneficially influenced.
A self-developing camera having a motor driven spread system and structure for inducing a bend in the film unit as it emerges from between the pressure-applying members is disclosed in U.S. Pat. No. 3,810,211 issued to R. R. Wareham, May 7, 1974. The camera is of a compact, folding, single lens reflex type and includes a housing section which extends forwardly of a pair of pressure-applying members. The housing includes a film exit slot therein which is out of alignment with the natural or normal emerging path of travel of the film unit. A deflecting plate is dispersed in the emerging path of travel of the film unit for deflecting the emerging film unit to induce the beneficial bend or curvature thereto and to guide it into the film exit slot. Thus, the pressure-applying members are substantially displaced from the exit slot and the mounting apparatus, for securing the pressure-applying members in a precise predetermined location within the housing in a secured operative relationship with the deflecting plate and exit slot, is critical to the distribution of the fluid processing composition within the element.
For example, in the first two aforementioned spread systems, the ultimate goal was to provide effective distribution of the fluid processing composition while requiring a substantially low pull force to advance the film unit between the pressure-applying members. These spread systems were scrutinized generally in terms of improving the ability of the user to withdraw the film unit comfortably, as determined by the rate of the roller biasing spring included upon the mounting apparatus. The pressure-applying members were adjacent and aligned with the exit slot which was substantially greater in width than that of the film unit and therefore not as critical in effecting the distribution of the processing composition. While precautions were taken, within limits, to prevent insufficient coverage due to mistracking or light spreading of the processing composition, such matters were generally under the control of the person withdrawing the film unit between the pressure-applying elements and complete control could not be developed or engineered into the spreader systems to combat human error. Therefore, the principal concern in the mounting apparatus was to substantially secure the spread system within the camera in alignment with the exit slot of the camera.
In the camera disclosed in U.S. Pat. No. 3,810,211, the bite line of the pressure-applying members is critical in determining the distribution of the processing composition and is a major concern in precisely positioning and securing the pressure-applying members relative to the deflecting plate anad the film exit slot. Incomplete spreads due to heavy concentrations of the processing composition early in the process and lean spreads leading to leakage due to the trap failing to have sufficient volume to receive the excess processing composition may lead to low quality photographic prints. For example, the spread system designed for use in the camera is engineered to provide a coating between the layers of the film unit of .+-.0.0002 inch of the nominal coating thickness. A coating exceeding the upper limit contributes to an imcomplete spreading and any value below the lower limit leans towards leakage and photographic prints having a red tint.
The mounting apparatus used to secure the pressure-applying members within the housing fixedly secures the spread system within the housing. Metal fasteners are used to fixedly secure the spread system to the housing. A torsion spring is joined to a frame mounted upon a floor of the housing and is coupled to each end of the bottom pressure-applying member to bias it in the direction of the upper pressure-applying member of the spread system. Highly precise piece parts, sequentially assembled, requiring multiple adjustments are characteristic in the mounting of the spreader system in its predetermined location relative to the deflecting plate and the film exit slot which greatly increases the cost of such piece parts, requires additional fixing tools in the hands of semi-skilled personnel and costly man hours in assembly and repair operations, which is not conducive to providing a low cost camera for the mass amateur market.
From the foregoing, it can be seen that there is a need for a mounting apparatus for a spreader system which is required to be precisely located in a predetermined location within a housing of a camera and securely retained without assistance from costly fasteners, staking or riveting and is readily adapted for relatively quick mounting and removal as an integral assembly from within the housing without undue thought and activity and with a substantial reduction in assembly operational costs. In a preferred embodiment, the mounting apparatus shall enable the spreader system to be located relative to the film receiving chamber for properly receiving an exposed film unit and initiate a developing processing therefor and further enable a housing section including a film exit slot to be attached to the spreader system for locating the housing section section and the film exit slot relative to the spreader assembly.